Bright nickel plating



Patented July 20, 1954 2,684,327 BRIGHT NICKEL PLATING Frank Passal, Detroit, Mich., assignor to United Chromium, Incorporated, New York, N. Y., a

corporation of Delaware No Drawing. Application November 2, 1951, Serial No. 254,629

14 Claims.

This invention relates to the electroplating of bright nickel, and more praticularly to brighteners for bright nickel plating baths.

The invention provides a bath for electroplat ing bright nickel having new and advantageous organic addition agents, functioning as brighteners, and to a process making use of such a bath.

Conventional baths and processes for electroplating bright nickel are described in Principles of Electroplating and Electroforming, Blum and Hogaboom, pages 362 to 381, revised third edition, 1949, McGraw-Hill Book 00., Inc New York; and in Modern Electroplating, The Electrochemical Society, 1942, pages 235 to 274. The character, control, and operating conditions, including the concentration of the bath ingredients, pH, temperature, cathode current density, etc., of these conventional baths are generally applicable to the present invention, It may be stated, in this connection, that practically all baths for electroplating bright nickel contain nickel sulphate, a chloride, usually nickel chloride, and a buffering agent, usually boric acid. Such types of baths include the well-known Watts type of bath and the high chloride type of bath. Other baths may contain, as the source of the nickel, a combination of nickel fiuoborate with nickel sulfate and nickel chloride or a com bination of nickel fiuoborate with nickel chloride.

Addition agents as brighteners in bright nickel plating baths may be generally divided into two separate classes on the basis of their-function in making possible the obtaining of truly bright deposits. One class, which is herein designated secondary brighteners, (1) increases the brightness of an ordinarily dull or matte deposit but not to a full or mirror bright stage and (2) imparts a ductilizing effect when used in conjunction with the other class of addition agents which are herein designated primary brighteners. The primary brighteners permit the obtaining oi mirror bright deposits when used in conjunction with secondary brighteners.

According to the present invention, novel and improved primary brighteners are provided and comprise indazole derivatives consisting of indazole having at least one substituent in its sixmembered ring. These derivatives have the structural formula:

7 24K x-os o-- c-n YO6 2NH \7/ \1/ c N in which the substituents W, X, Y, '01 Z on 'the number 4, 5, 6, or 7 carbon :atoms, respectively,

may be such radicals as the following: a radical which is linked to the six-membered ring through a nitrogen atom, that is, groups such as amino or substituted amino, nitro, sulfanilamido, p-tolu ene sulfanilamido, acylamido in which the acyl moiety preferably has a small number of carbon atoms, say up to six to ten, for example: acetamido, propionamido, butyramido, benzamido, etc; a radical which is connected to the said sixring through an oxygen atom, such as hydroxy and oxy-hydrocarbon groups, the latter being representable as OY (wherein O is an oxygen atom which is linked to the six ring and Y is a hydroearbon moiety) and including such groups as alkoxy, acyloxy, and acyl, in each of which the number of carbon atoms is small, preferably up to six to ten, and also including groups wherein Y is a cyclic, i. c. a cycloaliphatic or aromatic, moiety as well as an aliphatic moiety. The following examples are illustrative: methoxy, ethoxy, propoxy, butoxy, amoxy, phenoxy, benzyloxy, toloxy, acetoxy, propionoxy, butyroxy, capryloxy, benzoxy, acetyl, propionyl, butyryl, valeryl, caproyl, benzoyl, toluyl, furoyl, etc. Other substituent radicals for said six ring inc'lude halides like chloro and bromo; a radical linked to the six ring through sulfur, such as sulfonic acid and sulfonic acid salts of metals like sodium, potassium, nickel, etc.; and radicals linked to the six ring through carbon, such as alkyl, aryl, aralkyl, and heterocyclic groups, and including methyl, ethyl, propyl, butyl, amyl, hexyl, phenyl, tolyl, benzyl, phenethyl, iuryl. Preferably these groups should have a. small number of carbon. atoms, say up to six to ten. Other groups are carboxy and carbalkoxy.

Any one of the four substituents W, X, Y, or Z may be one of the foregoing groups while the remaining three substituents are hydrogen (H); or any two of the substituents may be chosen from the foregoing groups while the remaining two are hydrogen; or any three of these substituents may be chosen from said groups while the fourth is hydrogen; or all four substituents may be chosen from said groups.

Of these groups, those containing a nitrogen, oxygen, or sulfur atom linked to th six ring of the indazole moiety are preferred, such as nitro, amino, sulfanilamido, acylamido, hydroxy, sulfonic acid, and sulfonic acid salts.

The above structural formula, which represents the indazole moiety in the ortho-quinoid form, may also be written with the indazole moiety in the iso-indazole form, since in solution both forms may be present in a state of dynamic tautomerism. Some typical examples of the novel primary brighteners according to this invention are the following: 5-nitro-indazole, E-amino-indazole, 5sulfanilamido-indazole, 6- sul-fanilamido-indazole, 'I-sulfanilamido indazole,

S-indazole sulfonic acid, G-indazole sulfonic acid, 'Y-amino-indazole, 'Z-nitro-indazole, 7-amino-4 indazole sulfonic acid, 7-amino-4,5inolazole disulfonic acid, 4-chloro-5-nitro-indazole, 5-nitro 4-indazole sulfonic acid, 5-aminol-indazole sulfonic acid, 4-indazo1e sulfonic acid, '7-indazole sulfonic acid, 7 hydroxy in-dazole, 6 amino indazole, 6 amino 7 indazole sulfonic acid, 6-amino-5,7-indazole disulfonic acid, 6-chlorofi-phenoxy-indazolc, 5,6-dinitro-indazole, S-hydroXy-indazole, 'l-nitro-dndazole sulionic acid, 4 hydroxy indazole, 5 hydroxy indazole, 5- chloro-S-nitro-indazole, 6-aminol-indazole sulfonic acid, 6-nitro-7-chloro-indazole, 5-nitro-6- indazole sulfonic acid, 5-amino-6-indaaole sulfonic acid, 7-acetamido-indazole, l-nitro-T-acetamido-indazole, -l-amino-'7-acetan1ido indazole, 'l-amino 5 indazole sulfonic acid, initro-5- chloro 7 amino-indazole, 4-nitro-7-amino-5- indazole sulfonic acid.

The secondary brigh eners which can be used in conjunction with the above primary brighteners are substituted aromatic compounds in which the substituent comprises an SO2 containing moiety with the S atom linked to the aromatic moiety. These compounds have been designated aromatic sulfon-compounds, and they include naphthalene mono-, di-, or tri-sulfonates, a preferred class, either alone or in various mixtures. Salts of the foregoing compounds, such as the sodium or other alkali metal salts, are also preferred, although the compounds are useful in their acid form. Derivatives of the foregoing compounds, such as the chlorand alkoxy-substituted types, may serve. Benzene sulfonic acids and toluene sulfonic acids, their salts and their halogenated derivatives, and benzene sulionamides and toluene sulfonamides are other secondary brighteners. Still others are benzene sulfohydroxamio acid, o-benzoyl sulfimide (saccharin), and o-chloro-saccharin. Concentrations of the secondary brighteners are usually in the range or" 0.5 g./l. For example, naphthalene-1,5-disulfonate of sodium is useful at 5-10 g./i; naphthalene-1,3,6-trisulfonate of sodium, a preferred brightener, is used at 10-25 g./1.; saccharin at about l2 g./l.; p-toluene sulfonamide at 1-2 g./1.; benzene sulfohydroxamic acid at 0.2-5 g./l. In general, mixtures of the foregoing compounds may be used, as well as the individual D Nickel sulfate g./l 300 Nickel chloride g./l Boric acid g./l 38 Naphthalene-1,3,6-trisulfonate sodium g./l 20 5-nitro-indazcle g./l 0.015

Wetting agent, sodium lauryl sulphate type (Duponol PC) g./1 0.5 pH (electrometric) 3.5

4 Temperature F 130 Cathode current density amps. per sq. ft 30 Nickel sulfate g./l 300 Nickel chloride g-./l 45 Boric acid g./1 38 Naphthalene-1,3,6-trisulfonate of sodium g./l 20 5-amino-indazole g./1 0.015 Wetting agent, sodium lauryl sulphate type (Duponol PC) g./l 0.5 pH (electrometric) 3.5 Temperature F 130 Cathode current density amps. per sq. ft 30 III Nickel fiuoborate g./l 210 Nickel chloride g./l 45 Naphthalene-1,3,6-trisulfonate of sodium g./l 20 6sulfanilamido-indazole g./l 0.015

Wetting agent, sodium lauryl sulphate type (Duponol PC) g./l 0.5 pl-I (electrometric) 3.5 Temperature F 130 Cathode current densityarnps. per sq. ft- 30 Cathode agitation may be practised, the degree thereof to be determined by the type of work being nickel plated and the operating current density range desired. Excellent results have been obtained without any solution or cathode agitation by suitably regulating the current density range and temperature as per usual practice.

Due to the indazole moiety, the primary brighteners of this invention are organic bases and are appreciably soluble in acid electrolytes. They can, therefore, be added directly to the nickel plating bath or, preferably in the form of a stock solution prepared by dissolving the solid compound in water acidulateol with mineral acids such as sulfuric or hydrochloric acid.

The concentration of the primary brighteners in the nickel plating electrolyte may vary from about 0.005 to 0.05 gram per liter. A preferred concentration range is from 0.005 to 0.02 gram per liter, within which range excellent brightness and ductility of deposits can be obtained over a variety of basis metal surfaces such as steel, iron, copper and copper alloys, brass, bronze, and other suitable metals. The concentration of the other constituents of the bath may be varied to meet special requirements, as is conventional.

It is to be understood in this connection that the conventional baths and operating conditions disclosed in the publications cited above are incorporated here by reference, so that additional descriptions of these baths and operating conditions are unnecessary. However, the composition and concentration of one widely used bath may be illustrated, and that is one containing nickel sulfate, 200 to 300 g./l.; nickel chloride, 45 to g./l.; and boric acid, 37 to 45 g./l. The concentration of the secondary brightener (or ductilizing agent) and the wetting agent may vary over limits determined by the degree of ductility desired and by solubility considerations.

The primary brighteners of the invention, and particularly the indazole moiety, are resistant to chemical change and breakdown, such as may occur by virtue of oxidation or reduction reactions under bright nickel plating conditions.

Even when chemical changes occur, the resultant conversion or decomposition products have not been found to be harmful. The brighteners are compatible with other classes of addition agents of the kind usually employed in bright nickel plating baths. Further, they have been found to render the bath electrolyte less sensitive in certain respects, that is to say, these brighteners have the efiect of rendering the bath solution resistant to many organic and metallic contaminants, such as copper and zinc, that are apt to be encountered.

In regard to the operation of plating baths containing the foregoing primary brighteners, good levelling and smoothening action is possible, the degree of which is favorably influenced by the use of the present brighteners. The cathode current density and the temperature may be varied widely while yet obtaining highly lustrous, mirror bright deposits of nickel plate. The rate of brightening, or the increase of luster of the deposits with increase of thickness, is also favorably influenced, being superior to many presently used primary brighteners.

Advantages in the plated product are also apparent following the use of the present brighteners. Substantially pure nickel coatings are obtained that are ductile and have low internal stress and that are not appreciably embrittled by being subjected to the usual plating conditions.

Although the invention has been illustrated by certain selected embodiments, it will be appreciated that these are illustrative and that the invention is capable of obvious variations.

In the light of the foregoing description, the following is claimed.

I claim:

1. In an aqueous acidic bath solution for bright nickel plating containing at least one nickel salt as the source of the nickel and a substituted aromatic compound as a secondary brightener in which said substituent comprises an SO2 containing radical with the S atom linked to the aromatic ring of said compound, the combination therewith as a primary brightener of about 0.005 to 0.05 g.,/l. of an indazole derivative comprising indazole having a radical substituted in the six-membered ring thereof, said radical containing a non-metallic atom which is linked to said six-membered ring, and said non-metallic atom being selected from the group consisting of nitrogen, oxygen, sulfur, carbon, and halogen.

2. An aqueous bath solution according to claim 1 in which said radical contains a nitrogen atom linked to said six-membered ring.

3. An aqueous bath solution according to claim 1 in which said radical contains an oxygen atom, linked to said six-membered ring.

4. An aqueous bath solution according to claim 1 in which said radical contains a sulfur atom linked to said six-membered ring.

5. An aqueous bath solution according to claim 1 in which said radical contains a halogen atom linked to said six-membered ring.

6. An aqueous bath solution according to claim 1 in which said radical contains a carbon atom linked to said six-membered ring.

'7. An aqueous bath solution according to claim 1 in which said radical is an oxy-hydrocarbon radical having the oxygen atom thereof linked to said six-membered ring.

8. An aqueous bath solution according to claim 1 in which said radical is one selected from the class consisting of sulfonic acid and sulfonic acid salts and is linked to said six-membered ring through a sulfur atom.

9. In an aqueous acidic bath solution for bright nickel plating containing at least one nickel salt as the source of the nickel and a sulfonated aryl compound as a secondary brightener, the combination therewith as a primary brightener of about 0.005 to 0.05 g./1. of an indazole derivative comprising indazole having a radical substituted in the six-membered ring thereof, said radical being one selected from the class consisting of amino and substituted amino groups and which is linked to said six-membered ring through a nitrogen atom.

10. An aqueous bath solution according to claim 9 in which said radical is an amino radical.

11. An aqueous bath solution according to claim 9 in which said radical is a substituted amino radical.

12. In an aqueous acidic bath solution for bright nickel plating containing at least one nickel salt as the source of the nickel and a sulfonated aryl compound as a secondary brightener, the combination therewith as a primary brightener of about 0.005- to 0.05 g./l. of an indazole derivative comprising indazole having a hydroxy radical substituted in the six-membered ring thereof.

13. In an aqueous acidic bath solution for bright nickel plating containing at least one nickel salt as the source of the nickel and a sulfonated aryl compound as a secondary brightener, the combination therewith as a primary brightener of about 0.005 to 0.05 g./l. of an indazole derivative comprising indazole having a radical selected from the class consisting of sulfonic acid and sulfonic acid salts substituted in the six-membered ring thereof.

14. In an aqueous acidic bath solution for bright nickel plating containing at least one nickel salt as the source of the nickel and a substituted aromatic compound as a secondary brightener in which said substituent comprises an SO2 containing radical with the S atom linked to the aromatic ring of said compound, the combination therewith as a primary brightener of about 0.005 to 0.05 g./l. of an indazole derivative comprising indazole having a sulfanilamido radical substituted in the six-membered ring thereof.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,315,802 Lind et a1. Apr. 6, 1943 2,513,280 Brown July 4, 1950 

1. IN AN AQUEOUS ACIDIC BATH SOLUTION FOR BRIGHT NICKEL PLATING CONTAINING AT LEAST ONE NICKEL SALT AS THE SOURCE OF THE NICKEL AND A SUBSTITUTED AROMATIC COMPOUND AS A SECONDARY BRIGHTENER IN WHICH SAID SUBSTITUENT COMPRISES AN -SO2 CONTAINING RADICAL WITH THE S ATOM LINKED TO THE AROMATIC RING OF SAID COMPOUND, THE COMBINATION THEREWITH AS A PRIMARY BRIGHTENER OF ABOUT 0.005 TO 0.05 G./1. OF AN INDAZOLE DERIVATIVE COMPRISING INDAZOLE HAVING A RADICAL SUBSTITUTED IN THE SIX-MEMBERED RING THEREOF, SAID RADICAL CONTAINING A NON-METALLIC ATOM WHICH IS LINKED TO SAID SIX-MEMBERED RING, AND SAID NON-METALLIC ATOM BEING SELECTED FROM THE GROUP CONSISTING OF NITROGEN, OXYGEN, SULFUR, CARBON, AND HALOGEN. 